花生田施用绿僵菌对土壤微生物群落的影响

昆虫病原真菌绿僵菌对地下害虫防治具有良好应用前景，而大量释放绿僵菌可能引起土著微生物群落变化，从而影响其植物保护的综合效果。本文研究了花生播种期施用绿僵菌后，在根际和根围土壤中绿僵菌自身种群及土著细菌、真菌和放线菌种群的消长和群落结构变化。结果表明，绿僵菌种群在30 d内快速下降，之后降速减缓，以低密度持续存活。随花生生长，土壤微生物自身有消长过程，施用绿僵菌对放线菌影响最大、真菌其次、细菌最小，在根际的影响大于在根围的影响。分别地，绿僵菌处理对根际和根围细菌、根围真菌无显著影响；使根际真菌种群初期的下降速度减缓，到达谷底时间由15 d推迟到30 d，但回升速度加快，达峰顶由60 d提前到45 d，峰值降低1/3；绿僵菌明显抑制了根际放线菌种群，使其消长变化周期与对照完全相反，且45 d时回落至低点后不再回升；绿僵菌减缓了根围放线菌种群下降，使达谷底时间由30 d推迟到45 d，且回升幅度减小。土壤微生物群落结构在施菌后15～30 d的幼苗至初花期有明显变化，细菌种群总体占比显著下降，但与对照相比，施菌后的根际细菌占比提高，真菌占比下降，放线菌占比显著地先抑后扬。在根围的变化相对较小。45 d即盛花期后，三类微生物结构逐渐恢复趋近原来状态。

Effect of Metarhizium anisopliae as a Biocontrol Agent on Soil Microbial Community in Peanut Field

Metarhizium anisopliae, an entomopathogenic fungus, has been applied as a biocontrol agent to control soil-dwelling pests. The mass release of the fungus may change native microbial communities and impact the comprehensive effect of plant protection. In this paper, we investigated the population dynamic of applied M. anisopliae and native microbes including bacteria, fungi and actinomycetes in the soil of rhizosphere and root bulk after M. anisopliae treatment in peanut sowing period. The results showed that the applied M. anisopliae rapidly decreased within 30 days, then slowed down and continued to survive at low density. With peanut growing, the soil microbes exhibited their own process of ascending-and-descending population. In comparative, the applied M. anisopliae caused a greater influence on actinomycetes than on fungi, and minimal impact on bacteria. The effect on soil microorganisms was greater in rhizosphere than in root bulk. Separately, the M. anisopliae treatment had no significant effect on the bacteria in rhizosphere and root bulk as well as fungi in root bulk. However, the treatment slowed down the initially declining rate of fungal population in rhizosphere, that delayed the time to reach the bottom from 15 d to 30 d but after then accelerated the recovery rate. The peak was advanced from 60 d to 45 d but only reached 2/3 height of the control peak. For actinomycetes, M. anisopliae significantly inhibited the actinomycete population in the rhizosphere, making its fluctuation completely opposite to that of the control, and it did not rise again after falling to the low point on 45 days. In the soil of root bulk, M. anisopliae slowed down the declining rate of actinomycete population that delayed the time to reach the bottom from 30 d to 45 d and reduced the following recover numbers. The community structure of soil microbial was changed significantly in 15 d and 30 d after M. anisopliae treatment. The control proportion of bacterial population decreased significantly during this period. However, compared with the control, the proportion of rhizospheric bacteria increased and the proportion of fungi decreased, while the proportion of actinomycetes was significantly reduced first and then increased. The community structure was less varied in the root bulk. After 45 d, during peanut flowering, podging and maturity, the communities gradually recovered to the original state.